In aviation, airworthiness is the measure of an aircraft's suitability for safe flight. Initial airworthiness is demonstrated by a certificate of airworthiness issued by the civil aviation authority in the state in which the aircraft is registered, and continuing airworthiness is achieved by performing the required maintenance actions.
Blériot XI, civil registration G-AANG. Built in 1909 and operated by the Shuttleworth Collection in the United Kingdom, this is the world's oldest airworthy aircraft
Airworthiness certificate
A standard certificate of airworthiness is a permit for commercial passenger or cargo operation, issued for an aircraft by the civil aviation authority in the state/nation in which the aircraft is registered. For other aircraft such as crop-sprayers, a Special Airworthiness Certificate must be issued.
Interior of a Lockheed Super Constellation with a Special Airworthiness Certificate. The warning states "This aircraft is not required to comply with the safety regulations for standard aircraft. You fly in this aircraft at your own risk."